1. Field of the Invention
The present invention relates to a waveform signal processor effective in eliminating various random noise components contained in a cyclical waveform, and a device employing the waveform signal processsor. Random noise components are removed in preprocessing and the original signal waveform is extracted for output through digital processing. As examples of application, various types of waveform analyzers, oscilloscopes, and devices to measure the characteristics of recording media or heads can be cited.
2. Discussion of Background
Averaging processing is well known as a means for removing various random noise components contained in a cyclical waveform when digitally processing a cyclical waveform. The averaging processing is a method in which the cyclical waveform signal is sampled a plurality of times and the average of the sampling values obtained at the sampling points that correspond to the phases of the various cycles is determined. With this averaging processing, the noise components are practically removed.
In averaging processing, in order to improve the reliability of the obtained signal, it must be assured that the sampling points be the same for various cycles, and correspond to the same points on the time axis. In other words, the sampling points must correspond to the same phase when sampling the waveform to be measured. As a means for assuring this in the prior art, the average is taken by detecting the peak point, the zero cross point or the like, of a cyclical waveform, and by using this as a reference point on the time axis.
However, since the cyclical waveform which is the object of measurement contains various random noise components, the peak point or the zero cross point can vary due to these noise components. Because of this, it cannot be assured that the peak point or the zero cross point that is set as reference point on the time axis is, in fact, generated at precisely the same point on the time axis in each cycle.